CdS Films Research Articles

Efficient and recyclable photocatalytic degradation of methylene blue dye in aqueous solutions using nanostructured Cd1 − xCoxS films of different doping levels

This study outlines the impact of Co doping on the structures, morphologies, optical, and photochemical activities of nanoporous CdS films for efficient solar energy conversion. A sequence of nanotextured films of cadmium cobalt sulfide (Cd1 − xCoxS; where x = 0, 0.02, 0.04, 0.06, and 0.08) were grown on glass substrates using spray pyrolysis method followed by annealing at 300 °C for 2 h. The grown Cd1 − xCoxS films are of single wurtzite phase and polycrystalline nature. The preferential crystallographic growth of Cd1 − xCoxS nanocrystallites along the (002) is changed to (101) direction for x ≥ 0.06. The crystallite size and lattice parameters are decreased for x ≤ 0.04. Also, the absorption is increased and the optical bandgap is decreased to 2.40 eV at 6% Co-doping. The morphological study reveals the growth of agglomerated pure CdS nanorods. The incorporation of Co increases the density of nanorods, which self-assembled to form nanoporous surface at 2 and 4%. A random distribution of irregular nanorods accompanied by patterned spherical clusters is observed at 6%, which is assembled to a nanoporous pattern at 8%. The photocatalytic performances and reaction kinetics of the films are investigated for methylene blue dye decomposition under sunlight and artificial light illumination. The 6% Co-doped film reached the complete removal after 240 min under sunlight irradiation. This film showed higher stability than pure CdS film for 7 runs. Therefore, the combination of spray pyrolysis and adjustable doping level is a viable way for producing large-scale and reusable photocatalytic films for eco-friendly removal of dyes from industrial wastewater.

Heat-transfer ('iron-on') photocatalytic films

The simple preparation of nanoparticulate CdS and TiO2 photocatalytic (PC) films embedded in a thin (2.5 μm) layer of polystyrene (PS), i.e. PC-PS films, is described. These CdS-PS, or TiO2-PS, films are then readily and easily transferred onto a range of different common flexible materials, such as many different plastics and fabrics, using the heat from an iron. In all cases the heat-transferred PC-PS films appear physically robust, as demonstrated by the 3 M Scotch Tape test, and, for the same PC, exhibit a similar photocatalytic activity, regardless of the material it is ironed onto. The photocatalytic activities of these iron-on films are demonstrated using cotton as the material support. Thus, the CdS-PS-Cot film is used to photoreduce methyl orange, methyl viologen and water using visible light (415 nm) and a sacrificial electron donor (ascorbate or EDTA). The TiO2-PS-Cot film is used to effect the same reduction reactions, but with UVA light (365 nm). The TiO2-PS-Cot film is also able to photocatalyse the oxidation of methylene blue and NO by air. In most cases there is little or no loss of activity with repeated use. Encouragingly, the non-optimised TiO2-PS-Cot film appears more active than the commercial flexible polymeric photocatalytic film Purify Mesh 30 (Taiyo Europe GmbH).

An investigation of third-order nonlinear optical and limiting properties of spray pyrolysis-deposited Co:CdS nanostructures for optoelectronics

Cobalt (Co)-doped CdS thin films were deposited and successfully grown by the chemical reactive spray pyrolysis technique with different Co-doping levels [(Cd1−xCoxS) in ‘x’ ratios of 0.00, 0.01, 0.05 and 0.1 wt%] on heated glass substrates at 350 °C. The effect of Co content on nonlinear optical (NLO) properties was investigated by the DPSS continuous wave laser at 532 nm using the Z-scan technique. Powder-XRD analysis confirms the samples that have cubic structure with no impurity phases. The energy gap (Eg) of the prepared films was estimated and was found to be decreased by 2%, i.e., in the range from 2.50 to 2.30 eV. The room-temperature photoluminescence spectra were recorded at λexc = 275 nm and an intense blue emissions were observed at 430 ± 15 nm for undoped CdS and Co:CdS films. The Z-scan result reveals that reverse saturable absorption and self-defocusing nature are the attributed and observed nonlinearity of the prepared nanostructures. The nonlinear absorption coefficient, refractive index and third-order NLO susceptibility were determined and found in the range from 1.89 × 10−3 to 7.26 × 10−3 (cm W−1), 2.03 × 10−8 to 2.96 × 10−8 (cm2 W−1) and 1.21 × 10−6 to 6.95 × 10−6 (esu) correspondingly. An optical limiting topographies of the prepared films were explored and the limiting thresholds are also calculated at the experimental wavelength. These important results of NLO parameters are due to the increase in localized defect states on grain boundaries with the increase in Co-doping and suggest that these films are promising material for optoelectronic device applications.

A facile spray pyrolysis fabrication of Sm:CdS thin films for high-performance photodetector applications

Achievement of high-performance photodetectors based on CdS is a key field of research and challenge in the current scenario. Here, facile fabrication and characterization of novel samarium (1, 3 and 5 wt.% Sm)-doped CdS thin films for the photodetector applications have been demonstrated. The fabricated films show good crystallinity with crystallites size ranging 18–30 nm. The morphology and homogeneity of Sm-doping ingrown films were confirmed through scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX). Field emission SEM study reveals the low dimension nanograins formation and the films are free from voids and cracks. The effects of Sm-doping on linear and nonlinear optical properties of the fabricated thin films have been elucidated. The optical parameters such as refractive index, energy gap, susceptibilities were noticed to be reduced by Sm-doping in CdS thin films. An emission peak around 536 ± 14 nm was observed in PL spectra of pure CdS which was found to be shifted and quenched by Sm-doping. Finally, the photodetector performance of the fabricated thin films has been investigated for 532 nm laser light. The photodetector based on the 1 wt.% Sm:CdS shows an improved performance (higher responsivity of 1.01 AW−1, higher detectivity of 2.21 × 1012 Jones, excellent photosensitivity of ∼4.9 × 103, and very high external quantum efficiency (EQE) of 257 %) compared to pure CdS (responsivity of 0.213 AW−1, detectivity of 7.43 × 1011 Jones, photosensitivity of ∼2.0 × 103, and EQE of 249.70 %). These results propose a much simpler route to achieve high-quality CdS films for photodetector applications.

Effect of Triton X-100 surfactant on thiol-amine cosolvents assisted facile synthesized CdS thin films on glass substrate by spin coating method

In this article, the effect of Triton X-100 surfactant on the spin coated and vacuum annealed CdS thin films on glass substrates using thiol-amine cosolvents have been explored in details. The SEM study reveals that the surfactant assisted CdS films are uniform, homogeneous and smooth having less cracks, voids, pinholes compared to CdS films synthesized without surfactant. The X-ray diffraction spectra indicate the hexagonal structure of the surfactant-added films with (002) and (100) planes having relatively high intensity whereas a weak hexagonal (002) peak appears for the films deposited without surfactant. Two prominent Raman peaks of CdS thin films are observed at the wavenumber 207 and 212 cm−1 due to the multi-phonon vibration of hexagonal CdS. A relatively strong and broad FTIR peaks at 1647 and 670 cm−1 were observed due to the Cd-S bending and stretching vibration in the surfactant mediated films. Surfactant induced CdS films are nearly stoichiometric as manifested by the energy dispersive X-ray report. Finally, higher optical transmission and band gap have been achieved for the CdS thin films deposited with Triton X-100 surfactant. This study reveals that surfactant mediated CdS thin films with thiol-amine cosolvents can be exploited effectively in higher efficiency thin film solar cell technologies with low cost.

Structural and Morphological Characteristics of Organic and Inorganic Blend Heterojunction NiPcTs/CdS

In the present study NiPcTs, CdS thin films, and Blends of NiPcTs/CdS were prepared with 1:2 content mixing ratio of NiPcTs to CdS solutions. Cadmium chloride and thiourea were used as the essential materials for deposition CdS thin films while using organic powder of NiPcTs to deposit NiPcTs nanostructure films. The spin-coating technique was employed to fabricate the NiPcTs, CdS films, and NiPcTs-CdS blend. Structural properties of films have been investigated via X-Ray diffraction, and show that thin films of NiPcTs, and CdS have monoclinic and polycrystalline hexagonal structure respectively while the blend has two polycrystalline structure with cubic and hexagonal phases. Atomic force microscope (AFM) confirmed that the surface of all samples are quite smooth and they have comprised of spherical numerous nanoparticles with diameter less than 70 nm. Scanning Electron Microscopy (SEM), and energy dispersive spectroscopy (EDS)analyzer has been achieved to determine the chemical composition of the molecular materials, which exhibit the existence of all essential elements of thin films and blend heterojunction (BHJ) of NiPcTs -CdS. The preparation of chemical solutions, deposition of NiPcTs, CdS thin films and the blend heterojunction BHJ of NiPcTs–CdS have been characterized.

Fabrication and characterization of Sn:CdS films for optical-nonlinear-limiting applications

Herein, we are focusing on to inveterate physical properties of spray pyrolysis fabricated CdS films with diverse Sn doping contents (0.0, 0.5, 1.0, 2.5, 5.0 wt%) named as Sn:CdS. Hexagonal mono-phase of CdS at every content of Sn was detected by structural and vibrational analyses. The mean size of crystallites (Lave), density of dislocations, strain, number of unit cells and texture coefficient were estimated and the values of Lave are observed in 20–24 nm range. To confirm the presence of Sn and its homogeneity in films the EDX/SEM mapping was carried out. Fine nanostructured and pin hole/crack free films fabrication was suggested by SEM images. The grown Sn:CdS films are showing the transparency in 50–70% range in visible to INR range. The refractive index values were calculated in 1.6–2.9 range, over 500–2500 nm wavelength region. The estimated values of Eg are noticed in 2.43–2.45 eV range. At two excitation wavelengths the PL emission was recorded at both 350 and 450 nm excitation wavelength and possesses an emission at ~531 ± 20 and 530 ± 15 nm (green), correspondingly. The values of optical dielectric constant, conductivity, linear, third order- nonlinear susceptibilities and index of nonlinear refraction were estimated. Using a 650 nm wavelength laser the optical limiting was recorded and noticed to be strongly affected by Sn doping.

The effects of Zn incorporation on electrical, photoluminescence and spectral sensitivity of SILAR deposited CdS thin films

The SILAR deposited CdS films were incorporated with various concentrations of zinc using zinc acetate and zinc chloride precursors. The presence of zinc was found to alter the crystal structure and energy bandgap of the films. The bandgap increased by nearly 44% with the increase of zinc concentration in the films. The photoluminescence spectra of the films revealed the presence of several localized defects levels within the forbidden bandgap. The peak spectral response wavelength was found to vary from 500 nm to 400 nm with the increase of zinc. The photocurrent was found to increase with the Cd:Zn ratio. The films with relatively high concentrations of zinc were found to be better suited for the photodetector applications due to their higher photocurrent to dark current ratio.

A novel synthesis and characterization of transparent CdS thin films for CdTe/CdS solar cells

We demonstrate the direct synthesis of CdS thin films by spin coating method with thiol-amine co-solvents system. Annealing of the films at various temperatures has been performed in the air using simple glass protector. The XRD patterns show a strong peak along (110) plane related to cubic lattice while two weak peaks at (002) and (100) planes indicate the hexagonal symmetry for the CdS thin films. The Raman peak at 305 cm−1 also confirms the formation of crystalline CdS thin films. The FTIR study also reveals the formation of CdS thin films. The SEM images reveal the surface uniformity and homogeneity of the CdS thin films. The EDX results indicate nearly stoichiometric CdS thin films. The optical band gap of CdS thin films is ~ 2.4 eV when coated at 2000 rpm and annealed at 300 °C for 5 min. These findings indicate that synthesized CdS films are potential candidates for solution-processed CdTe/CdS solar cells.

Characterization of CdS sputtering deposition on low temperature pulsed electron deposition Cu(In,Ga)Se2 solar cells

The present paper reports the investigation of sputtered CdS as a buffer layer in Cu(In,Ga)Se2 (CIGS) solar cells, for a dry-low temperature all in-line production technology method. The CdS film is deposited using radio-frequency magnetron sputtering in argon atmosphere. Compared to the well-known CdS grown by chemical bath deposition, the sputtering technology is feasible for the serial manufacturing process. The morphology and optical transmittance of CdS thin films are studied, as well as the CdS/CIGS interface and the solar cell characteristic. We observe that CdS layer deposited on glass is uniform and continuous with optical transmittance above 90% in the wavelengths range corresponding to the energy gap of the absorber. Current density-voltage (J-V) curve shows an overall efficiency of 6% affected by inhomogeneity at the CIGS/CdS interface. Sputtering deposition is not able to create a homogeneous layer on the absorber irregularities due its growth process. Moreover, Auger depth profile shows oxygen contamination at the interface, due to absorber surface oxidation. Within this work, the main crucial aspects of a new solar cell production technology, as well as related solutions, are reported.

Single-step growth of high quality CIGS/CdS heterojunctions using Pulsed Laser Deposition

This work reports on the utilization of pulsed laser deposition (PLD) for the preparation of CdS thin films and CdS/Cu(In,Ga)Se2 heterojunction structures on soda-lime glass (SLG) and Mo-coated SLG substrates, respectively, under various process conditions. Single phase, stoichiometric and high optical quality CdS films are obtained at a fluence of 1.1 J/cm2 and at deposition temperatures of 200–400 °C. The results of this investigation were used to grow CdS on Cu(In,Ga)Se2/Mo/SLG. Both Cu(In,Ga)Se2 and CdS layers have been deposited sequentially using PLD without interrupting the deposition process. The influence of CdS deposition temperature on the properties of CdS/Cu(In,Ga)Se2 heterojunction has been extensively studied and is reported herein for the first time. Low series and high shunt resistances are obtained for the samples where CdS was grown at 200 and 300 °C. The CdS/Cu(In,Ga)Se2 diode grown at CdS deposition temperature of 300 °C exhibits the lowest ideality factor and leakage current, indicating the better quality of the diode. The results of this work demonstrate that high-quality CdS/Cu(In,Ga)Se2 diodes are obtained using pulsed laser deposition in a single-step growth process, eliminating the need for selenization of Cu(In,Ga)Se2 and the use of other growth techniques such as chemical bath deposition for CdS.

Influence of III–V substrates on the texture, structural, and optical properties of CdS thin films deposited by chemical bath deposition

We have studied the influence of texture distribution and crystalline structure of the CdS thin films on their optical properties. CdS samples were grown by chemical epitaxy on III–V substrates. Ga-V materials (c-GaAs and h-GaN) were selected due to the newly renovated interest in CdS/III–V heterostructures and their importance in the development of current optical devices, such as light emitter diodes and solar cells. Texture analysis was realized in pole diagrams obtained in a High-Resolution X-ray diffractometer. Measurements were carried out at 2θ = 26.6° and 2θ = 43.9° because these 2θ angles correspond to diffraction signal for cubic and hexagonal CdS phases, respectively. Pole diagrams show fourfold symmetry in the CdS layers deposited on GaAs (100) substrates and sixfold symmetry in CdS layers deposited on GaN (0002) substrates, which indicates that epitaxial CdS films with both crystal structures is possible by a low-cost technique (Chemical Bath Deposition). The structural study was completed with a surface analysis of the CdS samples by atomic force microscopy; the images obtained showed a greater surface roughness in the CdS layers grown on GaN substrates, this result agrees with the texture distribution observed in pole diagrams. Optical properties of radiative and non-radiative recombination were studied by Raman and photoluminescence (PL) spectroscopies. According to PL results, cubic CdS films have better efficiency in the recombination of radiative bands. In addition, we determined that the CdS–A1LO phonon for the cubic monocrystalline phase is located at 302.35 cm−1, which is 0.84 cm−1 smaller than hexagonal structure.

Optical properties of CdS:Pb thin layer deposited on glass substrate

The thermal evaporation technique has been used to deposit a polycrystalline cadmium lead sulphide thin film (Cd1-x PbxS with X=0.20) in a vacuum of about 10-5 Torr at 450 °C. This Cd1-x PbxS thin film has been investigated by X-ray diffraction technique. Optical constant like extinction coefficient (K), dielectric constant (€), and refractive index (n) have been measured from transmission spectrum in wavelength range from 700 nm to 1700 nm by manifacier’s envelope method. Crystallite size estimated from the Scherrer method has been found to be 31.25 nm. Coefficient of absorption (α) as well as film thickness (t) has been estimated by means of transmission spectra. The lattice parameter (a), dislocation density (δ), inter planner spacing (d), and micro strain (ε) have been calculated. X-ray study reveals that film stoichiometry is maintained in deposited film. The optical study confirms that optical band gap of Cd1-x PbxS film can be tuned from visible to near infrared region (2.42-1.20 eV) using relatively low cost technique. The red shift in optical band gap has been observed for Cd1-x PbxS thin film. Pb doping increase absorbance in visible region and near infrared region compared to undoped CdS film. The large decrease in band gap has been observed which makes the film much suitable for absorbing layer in solar cells, IR detector and other photovoltaic and optoelectronic applications. In film band, gap of 1.13 eV has been achieved which shows that doping of Pb in CdS makes it suitable material for solar cell absorber and IR detectors. The film shows high transmittance (about 70 %) in near infrared region. The film is polycrystalline and highly stoichiometric.

Effects of substrate temperature and SnO2 high resistive layer on Sb2Se3 thin film solar cells prepared by pulsed laser deposition

Sb2Se3, an emerging promising binary compound semiconductor, was prepared at different substrate temperatures by pulsed laser deposition for thin film solar cells for the first time. In this work, CdS and Sb2Se3 films were subsequently deposited by pulsed laser deposition to simplify the process. Film properties and device performance, closely related to the substrate temperature, were characterized by thermal gravimetric analysis, X-ray diffraction, UV–Vis–NIR spectrophotometer, scanning electron microscope, light and dark current density-voltage, external quantum efficiency and capacitance-voltage, respectively. Results indicate that Sb2Se3 solar cells film deposited at 500 °C is better, with a better efficiency of 3.58%. Furthermore, SnO2 high resistive layer was introduced into Sb2Se3 solar cell to improve the junction quality, leading to a champion device efficiency of 4.41%.

Influence of the CdCl2 Solution Concentration on the Properties of CdTe Thin Films

this work presents the influence of the concentration of CdCl 2 -treatment-solution on the microstructural, morphological, and optical properties of CdTe thin films. The CdTe films were deposited on CdS coated borosilicate glass by Close-Spaced Sublimation (CSS) technique using a standard recipe. The CdS films were grown by RF magnetron sputtering. The deposited CdTe films were treated with CdCl 2 solution of 0.20 M, 0.25 M, 0.30 M, 0.35 M, and 0.40 M concentration at 395 °C for 25 minutes. All the films exhibit polycrystalline nature with a predominant (111) Bragg peak of cubic CdTe. The highest crystallite size and smallest micro-strain and dislocation density are found for the treatment solution of 0.35M concentration. The results present that the treatment concentration enhances the S diffusion into the CdTe layer up to a certain limit of molar concentration. The highest S concentration (~2%) among the investigated samples are found for 0.35 M concentration. The SEM micrographs of the as-grown and treated films reveal that the grain size follows an increasing trend with the solution concentration up to 0.35 M. The optical bandgap of all samples are found to be in the range of 1.42 – 1.45 eV estimated from the UV-Vis-NIR transmission data. The lowest bandgap of 1.42 eV is found for the sample treated with 0.35 M solution due to the highest crystallinity among the samples investigated evident from both XRD and SEM results.

Fabrication and SILAR cycle-dependent characterization of CdS/p-Si heterojunction photodetector

We report the fabrication CdS/p-Si heterojunction via a successive ionic layer adsorption and reaction (SILAR) technique with different CdS thickness controlled by SILAR cycles. A brief investigation has been carried out to study the nano-structural, photodetecting and optical characteristics of prepared CdS/p-Si heterojunction. Structural and morphological characterizations confirmed the formation of crystalline hexagonal CdS thin films with nano-sized grain particles that develops closed packed with SILAR cycles. Photoluminescence (PL) have been studied that emission peak at 472 nm associated with excitonic emission and a broad green emission peak positioned at 553 nm from the recombination of S−2 vacancy with valence band of CdS film. Current–voltage (I–V) and optoelectronic properties of prepared samples presented the rectification properties having the ideality factor more than unity, while the peaks of response have two peaks located at 450 and 800 nm with maximum responsivity at 6 SILAR cycles.

Composition dependent structural, morphological, optical and electrical properties of CdS:Co window layer grown by chemical bath deposition

CdS as an n–type layer plays an important role in the fabrication of solar cells. Cd1-xCoxS thin-films with variable Co doping levels (x = 0 to 0.06) were deposited on glass and indium tin oxide-coated (ITO) glass substrates by simple and inexpensive chemical bath deposition. The effects of Co doping on the structural, optical, morphological, elemental, and vibrational properties of CdS films were systematically examined. XRD results revealed that Co concentrations increase and the crystallite size of the film decreases from 20.4 to 13.6 nm due to the incorporation Co in Cd sites. The optical bandgap was reduced from 2.44 to 2.32 eV due to the incorporation of Co, which was found with a UV–Vis spectrophotometer. Urbach energy, refractive index and extinction coefficient of all deposited films was estimated, and the results were discussed. The intensity of PL peaks was reduced by increasing the Co concentration in the red region. The resistivity and carrier concentration were measured from Hall measurement system and the film current density was increased from 7 to 26 mA/cm2 by cobalt doping.

Highly efficient and thermally stable Sb2Se3 solar cells based on a hexagonal CdS buffer layer by environmentally friendly interface optimization

A hexagonal CdS film is used to increase the quality and improve the spectral response of Sb2Se3 solar cells deposited by the RTE method. A 7.35% efficiency of Sb2Se3 solar cells has been obtained based on the hexagonal CdS film.

Низкотемпературный рост кубической фазы CdS методом атомно-слоевого осаждения на гибридных подложках SiC/Si

A new method has been developed for the epitaxial growth of cadmium sulfide CdS films in a metastable cubic phase on silicon substrates with a buffer layer of epitaxial silicon carbide by atomic layer deposition. This CdS phase is achieved due to the low growth temperature (~ 180 ℃). The cubic phase was identified by both X-ray diffraction (XRD) and spectral ellipsometry due to the fact that the main peak of CdS absorption is split into two peaks in the hexagonal phase (4.9 eV and 5.4 eV) and is a singlet in the cubic phase (5.1 eV).

Effect of the Dielectric Barrier Discharge Plasma on the Optical Properties of CDS Thin Film

Cadmium sulphide CdS films with 200 nm have been prepared by thermal evaporation technique on glass substrate at substrate room temperature under vacuum of 10-5mbar.In this paper, the effect of Dielectric Barrier Discharge plasma on the optical properties of the CdS film. The prepared films were exposed to different time intervals (0, 3, 5, 8) min. For every sample, the Absorption A, absorption coefficient α , energy gap Eg ,extinction coefficient K and dielectric constant ε were studied. It is found that the energy gap were decreased with exposure time, and absorption , Absorption coefficient, refractive index, extinction coefficient, dielectric constant increased with time of exposure to the plasma. Our study considers the first investigation of the effect of cold atmospheric plasma on the optical properties of CdS film.